The invention concerns an apparatus for simultaneously sterilizing a multiplicity of packs by means of a gas mixture containing hydrogen peroxide and a carrier gas, comprising
supply lines for the carrier gas and for hydrogen peroxide,
a device for evaporating hydrogen peroxide with heat and for mixing it into the carrier gas,
supply lines and a substantially horizontally extending distributor line, and
nozzles which are arranged above the respective pack and are connected to the distributor line.
It is known for upwardly open packs to be sterilized by introducing a mixture of air and gaseous hydrogen peroxide. With that known process a plurality of packs which are arranged in mutually side-by-side relationship in a row are simultaneously passed under the openings of a corresponding number of nozzles. The sterilization gas mixture is produced by hot air being passed through a porous tubular portion through which completely evaporated hydrogen peroxide is urged from the exterior and then mixed with the air. In addition, to avoid condensation of the sterilization agent, the mixture is passed through a supply and distributor line which is of a double-wall configuration and is charged with hot vapor.
The configuration of the lines with heated tube walls is expensive and difficult and complicated to produce and diffusion of the evaporated hydrogen peroxide in the sintered tubular member into the hot air also involves problems because very high pump pressures are required for the hydrogen peroxide and it is necessary to take precautions to ensure that pores of the right size are not blocked. Clogging of the pores can be expected when small pore sizes are involved while when excessively large pores are used the hydrogen peroxide is only inadequately evaporated.
Therefore the object of the present invention is to simplify the apparatus of the kind set forth in the opening part of this specification and at the same time to provide measures for keeping the concentration of hydrogen peroxide identical at all nozzles over the plurality of packs at a given time.
In accordance with the invention that object is attained in that the distributor line from the upstream location of the in-feed of the conditioned gas mixture to the location of entry upstream of the respective nozzle is in the form of a tubular body containing a longitudinal passage, with at least one substantially tubular heating cartridge extending over the length of the body, and distributed measurement locations, and that the heating cartridge is divided into at least two portions and can be heated controlledly by a supply of electrical energy in such a way that the temperature at the outer ends of the tubular body differs from that at the center and that preferably the temperature at the ends can be adjusted independently from the temperature at the center.
By virtue of the invention, in comparison with the state of the art, it is no longer necessary for the distributor line or indeed also the supply line to be of a double-wall configuration for heating the pipeline by means of passing hot vapor therethrough. It is sufficient to use a longitudinal passage with a heating cartridge which is arranged in the longitudinal direction thereof, in order to build up a given temperature profile in the longitudinal passage. It is understandably easier to provide a single-wall longitudinal passage or to provide same in a tubular body and at the same time arrange heating cartridges there. It has been found that it is also more desirable if the gas mixture, after it has been produced and introduced into the distributor line, is heated in the latter by means of heating cartridges, especially as a temperature profile of the desired magnitude is quite easy to build up, in accordance with the division of the heating cartridge into at least two portions. It was surprisingly found that the temperature of the gas mixture at the distributor line and in particular at the ends thereof causes a variation in the concentration of the peroxide in the gas phase. Therefore it is particularly preferred in accordance with the invention for the temperature at the outer ends of the tubular body to be lower than at the center thereof. By means of suitable heating of the heating cartridge in the center of the tubular body, it is possible to counteract a reduction, that is to say cooling of the gas mixture, at the necessary locations, with the consequence that the temperature at the outer end regions of the tubular body is lower than at the central region thereof, thereby surprisingly achieving both a temperature, which remains the same everywhere, of the gas mixture flowing out of the tubular body, and also a concentration, which remains the same everywhere, of the H2O2 contained therein.
With the sterilization apparatus according to the invention it is possible to simultaneously sterilize 5, 10 or 20 packs, that is to say to act thereon with the sterilization gas through the nozzles. As in the known case the packs to be sterilized are arranged in a row which is preferably in a straight line. The tubular body representing the distributor line then extends over that row of packs, that is to say it is in the form of an elongate rail or an elongate passage. Preferably the gas mixture produced is introduced at the center of the longitudinal extent of the tubular body and the latter is heated in such a way that the temperature of the gas decreases towards the outer ends of the tubular body. The invention provides for heating of the walls of the longitudinal passage in the central region and possibly also the entire tubular body in comparison with the outer ends thereof although the in-feed location of the gas mixture is in the central region. In accordance with the invention that avoids irregular heating and distribution of the concentration of the peroxide in the gas mixture.
In a specific preferred embodiment packs of a capacity of 0.5 liter, 1 liter and 1.5 liters have been respectively sterilized at the same time in tens. The overall volume flow of air for each 10 bottles was between 20 and 30 Nm3/h and particularly preferably 22 Nm3/h. The temperature of the air should be in the range of between 110xc2x0 and 150xc2x0 C. and should particularly preferably be 140xc2x0 C. 25% hydrogen peroxide was meteredly added in liquid form per cycle, that is to say for each 10 bottles, more specifically for the 0.5 liter pack between 0.5 and 1.0 ml, preferably 0.75 ml; for a 1 liter pack: between 1.0 and 1.5 ml, preferably 1.0 ml; and for a 1.5 liter pack: between 1.75 and 2.5 ml and particularly preferably 2.0 ml. As the volume flow for liquid hydrogen peroxide, a value of between 1.5 and 1.9 ml/s and particularly preferably 1.7 ml/s should be used. The gas concentration was in the range of between 50 and 93 g H2O2/Nm3 air and in particular in a desirable example it was 77 g H2O2/Nm3 of air.
In an advantageous configuration of the invention the tubular body is in the form of an elongate bar with a strong main body through which centrally passes a longitudinal bore forming the gas passage, with communicating openings to the nozzles, and which on opposite sides of the gas passage and at a spacing in relation to the gas passage is provided with outwardly open grooves for the insertion of a heating cartridge. Production of the distributor line is particularly simple with those measures for a tubular body which is built up in that way can be easily manufactured from a bar-like strong main body. It is only necessary to centrally provide a longitudinal bore in the longitudinal direction of the bar, the bore being provided with communicating openings, corresponding to the number of intended nozzles, transversely with respect to the longitudinal direction of the bar. The nozzles are then fitted in the region of those communicating openings, for example xe2x80x9cunderneathxe2x80x9d, on the tubular body and the main body because the sterilization gases and also other treatment agents in subsequent treatment stations of the overall machine are desirably introduced from above downwardly and, after having acting on the surfaces of the internal walls of the packs, can be sucked away upwardly again. Therefore the tubular body is arranged above the nozzles and they are disposed above the packs to be treated.
While the communicating openings with the nozzles are then provided in the bottom of the main body, in accordance with the invention a respective outwardly open groove is also arranged at opposite sides, that is to say laterally of the tubular body and the main body respectively, because one or more heating cartridges is/are then to be particularly easily arranged beside the longitudinal bore. In an outward direction clamping and pressure portions provide for closure and insulation in relation to dissipation of heat.
It is particularly desirable in accordance with the invention if each portion of the heating cartridge is heatable independently of the other. Such independent regulation of individual heating cartridge portions or each heating cartridge portion in relation to the adjacent portion means that it is possible to adjust the desired temperature profile, with the consequence that for example the temperature in the tubular body falls from the center outwardly. If, in the case of an apparatus which includes those features according to the invention, the temperature is measured at the respective nozzle end, then regulation is possible in such a way that the temperature of the gas at the nozzle end, at the moment of flowing out of same for the sterilization procedure, is the same in relation to all packs of the row which is just being treated. This means that the level of concentration of hydrogen peroxide is the same in all packs, with the consequence of identical sterilization.
It is further desirable in accordance with the invention if the respective nozzle is connected, preferably by way of a nozzle holding plate, to the communicating openings of the tubular body and is mounted to the latter and has a throttle opening. That throttle opening can be formed in different ways. It is disposed for example at the upstream intake side of the nozzle while the so-called spray holes are at the downstream end of the nozzle; in the case of a normal elongate nozzle there is a single spray hole. In the case of the last-mentioned embodiment of the elongate nozzle the throttle opening can even be identical to the spray hole and can be at the nozzle end. In another alternative embodiment in contrast the throttle opening can be at the upstream side and at a spacing from the nozzle end. In each embodiment however the respective nozzle should be provided with a throttle opening in order to cause a back-up of the gas mixture with the consequence that the throttling action and thus the pressure drop over the length of the gas passage are negligibly small. In contrast the throttle opening of the nozzle should produce a substantially greater pressure drop. In that way the volume flow of the gas mixture issuing from each nozzle is also influenced and is substantially identical when the teaching according to the invention is observed.
The apparatus according to the invention can be used to sterilize both upwardly open packs in the interior and also upwardly closed packs at the outside surface thereof. In the former case the throttle opening at the nozzle end can be downward while the openings and lines which are disposed upstream thereof have a substantially smaller throttle action because the passage openings are larger.
In the case of the second-mentioned embodiment in which for example a pack in the form of a bottle is still closed in its upper screwthreaded neck region and is sterilized from the exterior, equality of the volume flows issuing from the individual nozzles is achieved by a throttle opening in an aperture plate which is arranged in the region of the entry location of the conditioned gas mixture between the distributor line and the nozzle. That entry location can preferably be in the region of the respective communicating opening to the nozzles.
In that embodiment of the sterilization apparatus according to the invention, in which upwardly open packs are sterilized in the interior thereof, the respective nozzle of the nozzles which are disposed fixed in a row under the tubular body is provided with a fixing flange at the top for mounting to a nozzle holding plate and with a further elongate through-flow passage which extends approximately over two thirds of the nozzle length, and in the region of the nozzle end with a narrower discharge passage which at the same time performs the function of the throttle opening. In this embodiment the edge of the respective upwardly open pack is held vertically at a spacing below the lower nozzle end. In that way the packs can be transported horizontally past the nozzles therebeneath. Annular suction devices can also be provided at the outer periphery of the lower nozzle end in order to receive, suck away and carry off the discharge gases which issue from the interior of the packs which have been subjected to the action of sterilizing gas.
There are also packs which are in the form of a bottle and which at the top have an opening on the bottle neck, which is provided with a male screwthread. In the production of such bottles which usually comprise HDPE and are produced by an extrusion blow molding process the bottle is internally sterile after manufacture and the opening at the bottle neck at the top is still closed in that intermediate stage by a dome which is cut off in a later processing station. In the region of the cut, no contamination is to pass into the interior of such a pack. It is therefore preferable to sterilize the external surfaces in the region of the bottle neck and the dome thereabove, while the pack is still in a closed condition. Accordingly, in accordance with the invention, the nozzle has an internal space which at least partially embraces the regions of the pack to be sterilized and which is delimited by a channel-shaped spray passage which is open on opposite sides and provided with spray holes, and outside walls which are arranged at a spacing from the spray passage and which are also laterally partially open. It has already been mentioned above that, in this embodiment, the throttle opening of the nozzle is at the top at the entry location of the conditioned gas mixture in the region of the communicating opening. The above-mentioned annular spray passage is disposed at a spacing from the above-mentioned throttle opening or aperture beneath and within outside walls and at a spacing therefrom. The spray passage is provided with spray holes in that region in which the pack to be sterilized comes to a stop for the treatment. In other words, the spray holes are admittedly at least partially also in the channel at the top, but preferably and primarily on opposite sides of the channel walls. On the other two sides the channel is open on opposite sides, and for that reason this involves a spray passage in the form of a channel. More specifically, the upper closed part of the pack engages into that channel and is passed along the channel, intermittently stopped in the region of the spray holes and then continues its movement, depending on when the row of packs is moved to the nozzle and further conveyed along after treatment.
For the treatment of this embodiment of the upwardly closed packs, preferably the bottles which are still closed at the top at the bottle neck with a dome, the upper region of that pack engages into the channel-shaped spray passage. That spray passage delimits the internal space into which the upper part of the pack engages, in which case the internal space therefore embraces the upper part of the pack. The upper part of the pack is to be externally sterilized. The external walls of the nozzle are disposed at a spacing from the channel walls of the spray passage outwardly transversely with respect to the longitudinal direction of the channel so that a space is respectively formed outwardly behind the spray nozzles, through which space the conditioned gas mixture can be passed from the upstream region of the nozzle through the spray holes to the pack surface which is to be sterilized.
After the spraying operation the gas mixture which has been used up flows away outwardly on the one hand at the lower edge of the spray passage, preferably above a bottle holding plate if such is provided, and also flows away outwardly along the spray passage. There the component of the gas mixture which has either not been used or consumed can be drawn off and collected for re-processing.
It is further desirable in accordance with the invention if the device for evaporating hydrogen peroxide with heat and for mixing it into the carrier gas has an atomization nozzle which is fed by a supply line for liquid hydrogen peroxide and which is arranged in the central region of an evaporation chamber upstream of a heating body, to the upstream hot surface of which hydrogen peroxide is fed in mist form with mixing with hot carrier gas and is passed through passages into the heating body in such a way that super-heating of the gas mixture is effected before being fed into the distributor line. Therefore, to produce and condition the sterilizing gas mixture, gaseous hydrogen peroxide is mixed with carrier gas, preferably hot sterile air, and then fed to the respective nozzle. That procedure for producing and conditioning the gas mixture is initially effected centrally in the above-mentioned evaporation and mixing device. In the preferred embodiment which is being discussed here, the evaporation and mixing device is a heating body with an evaporation chamber connected upstream thereof. Hot air is supplied by way of pumps to the evaporation chamber which for example can be mounted like an inverted funnel on a flat hot surface of the heating body. Disposed approximately at the center of that evaporation chamber is the downstream end of an atomization nozzle to which liquid hydrogen peroxide is fed. That H2O2 mist is firstly mixed with the hot air and then passes onto the above-mentioned flat hot surface, evaporates and is finally heated in the passages in the heating body. Thereafter the gas mixture is conditioned and can be fed centrally to the tubular body and thereafter along same to the individual nozzles.
In the case of such a conditioning process the sterilizing agent is firstly sprayed onto the above-mentioned hot surface which is at a first temperature. That surface is smaller than that at which film boiling begins. More specifically the gas mixture is deposited in the form of a film and then begins to boil on those surfaces. The heating body permits super-heating of the sterilizing agent which is passed downwardly from the above-mentioned hot surface along the passages in the heating body. In counterflow relationship therewith, that is to say from below upwardly, a heat flow can be produced in the heating body, which provides for the super-heating effect.
For that purpose it is desirable if, in accordance with the invention, some heating bars are inserted in the downstream end region of the heating body.
With the sterilizing apparatus according to the invention the sterilizing agentxe2x80x94as mentioned hereinbeforexe2x80x94is brought into contact with the upper hot surface of the heating body by being sprayed thereon in mist form. It is therefore not a liquid (the sterilizing mixture) that comes into contact with the upper hot surface, but only a mist of the sterilizing agent, that is to say a large number of finely distributed droplets. That provides that the effective surface area of the liquid sterilizing agent is considerably increased and the transfer of heat from the hot surface to the respective liquid droplet improved.
So that atomization at the end of the atomization nozzle can be successfully implemented, a further configuration of the invention provides that the supply line for liquid hydrogen peroxide is cooled by a cooling fluid. Preferably the atomization nozzle which is of an elongate configuration and which extends from its supply location into the center of the evaporation chamber can be externally provided with a casing through which coolant, for example water, flows. The technical production of such an externally cooled elongate nozzle can be satisfactorily managed without problems.
The insertion of tubular heating bars, for example from below into the downstream end region of the heating body, is also technically free from problems. It is possible in that way to produce a thermal gradient from below upwardly and thus a flow of heat in the heating body which is in opposite relationship to the flow of the gas mixture undergoing evaporation. In that way it is possible to achieve effective super-heating of the sterilizing gas, with sparing use of energy. In that respect consideration should always be given to the recommendation according to the invention that the downstream end of the atomization nozzle is disposed at a spacing from the walls of the evaporation chamber, that is to say the hydrogen peroxide mist is not sprayed onto a wall but is sprayed freely into the space of the evaporation chamber.
Even if PET and HDPE packs are sterilized by means of hydrogen peroxide the existing hygiene and health conditions are satisfied. It is possible to keep the residual H2O2 amount in PET-bottles filled with liquid below 0.5 ppm.
In regard to the manufacture, sterilization, filling and closure of packs using the apparatus according to the invention, in the case of a particularly preferred powerful machine, the cycle time involved was about 5.7 seconds, including the transportation time from one station to another. The respective pack is therefore resident for between about 4.5 and 5.5 seconds under the nozzle, in a specific embodiment that time was 4.7 seconds.
At the ends of ten nozzles arranged in succession in a row, temperatures were attained which deviated less than 10xc2x0 C. from each other, with highest temperatures of 143xc2x0 C. and lowest temperatures of 134xc2x0 C. in a preferred embodiment.